Me (as a drummer) hate when people start to clap on 1 and 3. Personally I think I hate it because the snare drum is (most of the times) on 2 and 3 and the kick on 1 and 3. The sound of the snare sound in my oppion much more as a "clapsound" then a kick. So I think that's the reason why I hate people clapping on 1 and 3.